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Others facing quarantine include those sitting close to travelers with symptoms, those with elevated temperatures and those from areas where virus outbreaks have occurred.

A 15-year-old from Topeka, Kansas, told CNN on Monday that she was quarantined in Beijing for a week.

"Apparently, I was sitting too close to a man who had a fever on the 14-hour plane ride," Kaitlin Hannigan said, adding that she initially thought she had a fever, but her temperature was fine when officials checked it.

A day after she arrived in Beijing with an educational group, government officials showed up at her hotel.

"They were wearing quarantine suits, goggles and masks and, like, full body suits and gloves, and said I had to be quarantined for seven days because I came in contact with that guy," Hannigan said.

Earlier in June, New Orleans, Louisiana, Mayor Ray Nagin was quarantined in Shanghai after possible exposure to the virus.

Nagin was headed to Australia on an economic development trip when he was quarantined for four days after sitting beside a passenger who was being treated for suspected swine flu symptoms. Nagin showed no signs of illness.

State officials warned Americans traveling to China that they have to follow local quarantines procedures.

"The U.S. Embassy will be unable to influence the duration of stay in quarantine for affected travelers," the statement said.